Data storage systems are known which include a plurality of heads adapted to read or write data to a plurality of discs of a disc stack. The plurality of discs or disc stack are supported for co-rotation on a spindle assembly. The spindle assembly includes a spindle hub rotatable about a spindle shaft. The disc stack is supported on the spindle hub to rotate about the spindle shaft for operation via operation of a spindle motor as is known.
Heads are supported relative to the rotating discs to read or write data to the rotating discs. Accurate placement of the head relative to the disc surface is important for seek commands and track following for read-write operations. Various factors affect placement of the heads relative to the disc surface. For example, dynamic imbalance of the spindle assembly can affect track seek and following. Variations in the mass distribution of the spindle hub can affect dynamic balance of the spindle assembly. The present invention addresses these and other problems and provides advantages and solutions not previously recognized.